Flat panel optical display systems, such as liquid crystal displays, are well known and widely used. Many such displays (e.g., liquid crystal displays) require polarized illumination light. Typically, polarization of illumination light greatly attenuates the light, thereby resulting in displays with decreased brightness, or require relatively expensive optical components. Moreover, such displays commonly have relatively low contrast ratios, which decreases image clarity and overall image quality. Furthermore, such displays typically require complex or difficult manufacturing processes.
To address such shortcomings, the present invention includes a microelectrical mechanical optical display system that employs microelectrical mechanical system (MEMS) actuators to modulate light. As is known in the art, MEMS actuators provide control of very small components that are formed on semiconductor substrates by conventional semiconductor (e.g., CMOS) fabrication processes. MEMS systems and actuators are sometimes referred to as micromachined systems-on-a-chip.
In one implementation, a MEMS optical display system according to the present invention includes an illumination source for providing illumination light, a collimating lens for receiving the illumination light and forming from it collimated illumination light, and a microlens array having an array of lenslets and receiving the illumination light from the collimating lens. The converging microlens array directs the illumination light an array of pixel apertures in an aperture plate to a microelectrical mechanical reflector array positioned opposite the aperture plate.
The microelectrical mechanical reflector array includes an array of microelectrical mechanical actuators that support reflectors in alignment with the array of pixel apertures. The array of microelectrical mechanical actuators orient the reflectors selectively to direct the illumination light back through the pixel apertures (to form part of a display image) or against the aperture plate (to be blocked). The illumination light passing back through the pixel apertures pass through the microlens array and a beamsplitter to a display screen.
A MEMS optical display system according to the present invention is operable without polarized illumination light, thereby eliminating the light attenuation or expense of the polarizing illumination light. In addition, light can be completely blocked or modulated by cooperation between the MEMS reflectors and the aperture plate, thereby providing display images with very high contrast ratios. Furthermore, such MEMS actuators can be manufactured by conventional CMOS circuit manufacturing processes.
Additional objects and advantages of the present invention will be apparent from the detailed description of the preferred embodiment thereof, which proceeds with reference to the accompanying drawings.